1. Field of the Invention
The present invention relates to filtration equipment using a hollow fiber module(s), which is used to filter fluids, or liquids, such as condensate water, obtained in a nuclear or thermoelectric power plant, and waste water, and particularly to the structure of a fixture for a hollow fiber module to be vertically installed in a filter vessel while enabling the filtrate to be collected from both the top and bottom ends of the hollow fiber module. The present invention further relates to a hoisting accessory not only for easily installing a long hollow fiber module in a filter vessel but also for easily removing the hollow fiber module upward from the filter vessel.
2. Related Art
In conventional filtration equipment using hollow fiber modules, the hollow fiber modules are simply suspended from a watertight partition, or module support, horizontally disposed in a filter vessel, wherein the filtrate is collected on the upper side of the hollow fiber modules and then withdrawn, or discharged, out of the filter vessel.
More specifically, each of the hollow fiber modules used in the conventional filtration equipment comprises a large number of porous hollow fibers having open top and bottom ends and enclosed in a cylindrical housing having the bottom end thereof covered by a lower header, or lower manifold, defining a lower filtrate collection chamber having no outlet port, and the cylindrical housing has a number of perforations formed through the longitudinal wall thereof for passing feed water therethrough. The filter vessel is partitioned with the watertight partition horizontally disposed therein to form a common upper filtrate collection compartment provided for all the hollow fiber modules and disposed on the upper side of the hollow fiber modules. Feed water entering the cylindrical housings of the hollow fiber modules through their perforations is allowed to permeate porous hollow fibers substantially all over the longitudinal length thereof by means of a hydraulic pressure to thereby effect filtration of the feed water through the walls, or membranes, of the porous hollow fibers into the bores thereof, through which the filtrate is then moved simultaneously downward and upward and then collected in the respective lower filtrate collection chambers of the hollow fiber modules and the common upper filtrate collection compartment. Every hollow fiber module is provided with a conduit, or central tube, extending from the lower filtrate collection chamber thereof to the common upper filtrate collection compartment. The filtrate collected in the lower filtrate collection chambers of the hollow fiber modules is transported, or shunted, therefrom through the conduits of the hollow fiber modules to the common upper filtrate collection compartment. Accordingly, all the filtrate is withdrawn, or discharged, out of the filter vessel via the above-mentioned common upper filtrate collection compartment located in the upper part of the filter vessel.
Thus, the foregoing conventional filtration equipment using the hollow fiber modules, though it is of a system wherein the filtrate is collected from both ends of every porous hollow fiber, necessitates the comparatively thin conduits, or central tubes, running from the respective lower filtrate collection chambers of the hollow fiber modules to the top ends thereof to transport, or shunt, the filtrate collected in the lower filtrate collection chambers into the common upper filtrate collection compartment.
This entails addition of a pressure loss through the conduits to the resistance of the membranes of the porous hollow fibers to permeation of water. As a result, the outer membrane surfaces of the upper portions of the porous hollow fibers are more liable to fouling than the outer membrane surfaces of the lower portions of the porous hollow fibers. Hence, it is impossible efficiently to use the porous hollow fibers substantially all over the longitudinal length thereof. Further, since the conduits are provided inside the respective hollow fiber modules, spaces occupied by the conduits cannot be filled with porous hollow fibers to lower the filtration efficiency of the hollow fiber modules.
A filter vessel designed to solve the foregoing problems was proposed, which comprises upper and lower watertight partitions horizontally disposed in the filter vessel to form upper, intermediate and lower compartments, and a plurality of hollow fiber modules installed in the intermediate compartment, and wherein feed water fed into the intermediate compartment is filtered through the walls of porous hollow fibers in the hollow fiber modules, while the filtrate is collected simultaneously into the upper and lower compartments via the open top and bottom ends of the porous hollow fibers and then discharged from the upper and lower compartments out of the filter vessel (Japanese Patent Laid-Open No. 197,106/1987). In this filter vessel, however, each hollow fiber module is watertightly joined with a lower filtrate collection tube thrusted through the lower watertight partition by means of a connector to communicate with the lower compartment via the lower filtrate collection tube. This joining work is very troublesome and requires skilled workmen. Furthermore, the hollow fiber modules, lower filtrate collection tubes, connectors, etc. must be very high in dimensional accuracy because the hollow fiber modules are watertightly fixed between the upper watertight partition and the respective lower filtrate collection tubes by means of the respective connectors. Moreover, elongation or shrinkage of the hollow fiber modules, the lower filtrate collection tubes, etc. due to a change in temperature sometimes makes it troublesome not only to install but also to remove the hollow fiber modules.
Accordingly, an object of the present invention is to provide filtration equipment wherein a hollow fiber module(s) can be easily installed in a filter vessel and easily removed from the filter vessel, and wherein porous hollow fibers can be efficiently used substantially all over the longitudinal length thereof and the filtration efficiency of the hollow fiber module(s) can be enhanced.
A hollow fiber module is such a long element as to be poor in workability and make the handling thereof dangerous. Accordingly, another object of the present invention is to provide a hoisting accessory for enabling installation and removal of a hollow fiber module to be quickly, more easily and safely carried out.